The present invention relates generally to a means for regulating the high pressure component of a transcritical vapor compression system.
Chlorine containing refrigerants have been phased out in most of the world due to their ozone destroying potential. Hydrofluoro carbons (HFCs) have been used as replacement refrigerants, but these refrigerants still have high global warming potential. xe2x80x9cNaturalxe2x80x9d refrigerants, such as carbon dioxide and propane, have been proposed as replacement fluids. Unfortunately, there are problems with the use of many of these fluids as well. Carbon dioxide has a low critical point, which causes most air conditioning systems utilizing carbon dioxide as a refrigerant to run transcritical under most conditions.
When a vapor compression system is run transcritical, it is advantageous to regulate the high pressure component of the system. By regulating the high pressure of the system, the capacity and/or efficiency of the system can be controlled and optimized. Increasing the high pressure of the system (gas cooler pressure) lowers the specific enthalpy of the refrigerant entering the evaporator and increases capacity. However, more energy is expended because the compressor must work harder. It is advantageous to find the optimal high pressure of the system, which changes as operating conditions change. By regulating the high pressure component of the system, the optimal high pressure can be selected.
Hence, there is a need in the art for a means for regulating the high pressure component of a transcritical vapor compression system.
The present invention relates to a means for regulating the high pressure component of a transcritical vapor compression system.
A vapor compression system consists of a compressor, a heat rejection heat exchanger, an expansion device, and a heat absorbing heat exchanger. The high pressure of the system is regulated by a controllable valve connected at the exit of one or more gas cooler circuits. In a preferred embodiment of the invention, carbon dioxide is used as the refrigerant.
This invention regulates high pressure component of the vapor compression (pressure in the gas cooler) by controlling the actuation of a valve located at the exit of one or more of the gas cooler circuits. Closing the valve turns one of the circuits into a dead end volume which accumulates and stores charge, reducing the effective heat transfer area and increasing the gas cooler pressure. Opening the valve releases charge and the gas cooler pressure is reduced.
By controlling the actuation of the valves, the high pressure component of the system is regulated, controlling the enthalpy of the system to achieve optimal efficiency and/or capacity.
Accordingly, the present invention provides a method and system for regulating the high pressure component of a transcritical vapor compression system.